In the development of power supplies and power management for computer systems, as in most technologies, new concepts and products bring with them new problems, and sometimes older problems are exacerbated. Supplying power to CPUs on computer motherboards is a case in point.
As CPUs have gotten faster and more powerful, they have also increased in load requirements and in total power consumed. Moreover, efforts have been made to reduce the voltage required for microprocessors used in and for CPUs. At lower voltage, such as 3.3 volts now required by some commercially available microprocessors, instead of the traditional 5 volts, voltage regulation becomes more important.
Voltage regulation is more important with newer microprocessors also because of the higher power, hence higher current, and the speed with which events transpire in modern computers. A high-power microprocessor suddenly activated, with immediate processing activity as well, generates a relatively high rate of change of current with respect to time, which can (and does) seriously effect the voltage supplied, unless adequate steps are taken to avoid or manage the transient circumstances.
In current art there are three fundamental implementations of variable-voltage CPU voltage regulators:
1. Regulator in power supply. This implementation is not accurate, its cross-regulation is not good, and on line losses are too high. PA1 2. Line regulator on motherboard. This method is cost effective, but efficiency is low and reaction speed is poor. PA1 3. Switching regulator on motherboard. Efficiency improves, but the cost is high and reaction speed remains poor.
FIG. 1 shows a voltage regulator and dual-voltage CPU in current technology. A power source (the power supply unit) supplies 12-volt and 5-volt output. A 5-volt CPU uses power directly from the PSU. A 3.3-volt CPU requires conversion through the voltage regulator.
In all current art, the best accuracy without manual adjustment is 3% or worse. Improving accuracy below a 3% tolerance increases the cost unacceptably and needs continual manual adjustment-not acceptable requirements in a personal computer.
FIG. 3 shows details of a switching voltage regulator chip with a resistor or potentiometer, as used in current art.
What is clearly needed is improved methods and apparatus for regulating voltage to CPUs to improve regulation, control line losses, improve reaction time (speed), and to improve efficiency.